Chrome tanning process



Patented Nov. 27, 1934 UNITED STATES PATENT OFFICE CHROME TANNINGPROCESS waukee. Wis.

No Drawing. Application March 5, 1927, Serial No. 173,217

10 Claims.

The present invention relates to a chrome taming process for convertinga skin or hide into leather.

According to the ordinary chrome tanning process, the skin or hide isfirst softened and cleansed and then its flesh and hair are removed.

The skin or hide is treated with lime to loosen its hair and therebyfacilitate the removal thereof.

After the skin or hide has had its hair removed, it is treated with acidor bate to remove at least its surface lime, and then it is pickled inacid and salt to bring it into condition for chrome tanning.

The present invention has for its object to shorten the time required toprepare the skin or hide for chrome tanning and to convert it intoleather by chrome tanning.

Another object is to set and fix the tannable substance in the skin orhide at a rapid rate upon commencing the tanning thereof.

Another object is to retain in the skin or hide for conversion intoleather tannable substance before lost in deliming and pickling the skinor hide.

Another object is to lessen the loss of tannable substance from the hidein preparing it for tanning and in commencing the tanning thereof.

Another object is to obviate pickling the skin or hide before commencingthe chrome tanning thereof.

Another object is to increase by weight and area the leather yieldedfrom a skin or hide.

Another object is to provide plump and fine grained leather.

Another object is to provide an expeditious and economical chrometanning process.

According to the present invention as it has been performed in practice,the skin or hide after its flesh and hair have been removed and itssurface has been delimed, is subjected to pretanning in a pretanningliquor containing a mixture of aldehyde, mineral acid, and salt untilits tannable substance is set and fixed and conversion thereof intoleather commences, and then the skin or hide thus pretanned is subjectedto final tanning in chrome tanning liquor until it is converted intoleather.

The skin or hide need only be surface delimed before commencing thepretanning thereof as the pretanning liquor will remove the remaininglime and place the hide in condition for chrome tanning.

In order to further explain the invention, an example thereof as it isordinarily performed in practice will now be explained.

The skin or hide, after it has been limed and its hair has been removed,is surface delimed by a deliming agent and then subjected to pretannageuntil its tannable substance is fixed or set and conversion thereof intoleather com- 00 mences.

The pretanning liquor by which the pretanning of the hide is effected isa mixture of an aidehyde, for instance, formaldehyde, such as isordinarily employed as a tanning agent, sulphuric as acid, neutral salt,and chromic oxide salt.

The essential ingredients or constituents of the pretanning liquor arethe aldehyde and the acid.

As the pretanning liquor is a mixture of its ingredients orconstituents, the quantities and proportons of these ingredients orconstituents may be varied through a wide range.

The effect of the pretanning liquor upon the hide is the resultanteffect of the individual action of each of its ingredients orconstituents.

The formaldehyde is a tanning agent which fixes and sets the tannablesubstance in the hide at a rapid rate to lessen the loss thereof fromthe hide, and it further acts upon the tannable substance in the hide tocommence conversion thereof into leather. I

The lime remaining in the hide after it has been surface delimed isneutralized and dissolved by the sulphuric acid and then eliminated fromthe hide into the pretanning liquor.

If the formaldehyde were in a neutral or alkaline condition, it wouldtend to surface harden the hide by its astringent action thereon, andthat would impede the diffusion of theformaldehyde into the hide and theinitial and final tanning of the interior of the hide.

The sulphuric acid in the pretanning liquor keeps the hide in conditionfor the formaldehyde and chromic oxide salt to readily diffuse into thehide and throughout the interior thereof.

When the hide has been pretanned in the pretanning liquor, it is incondition for the final chrome tanning liquor to readily diffuse intoits interior and thereby convert it throughout into leather, v

As the chromium or chromic oxide salt is a chrome tanning agent, itcommences the chrome tanning in the pretanning of the hide.

The sulphuric acid tends to plump and swell the hide, but this effect iscounteracted by the neutral salt and also the chromic oxide salt.

As the hide is only surface delimed before commencing the pretanningthereof, tannable substance before lost in deliming and pickling the nhide is retained in the hide and converted into leather.

When the hide has had its tannable substance fixed and set andconversion thereof into leather has commenced, the pretanning isdiscontinued and then the hide is subjected to final tanning in a chrometanning liquor in the ordinary way until it is converted into leather.

The time required for the pretanning is of the order of from one-half tothree hours.

The chrome tanning may commence immediately after the pretanning and thetime required therefor is of the order of from two to ten hours.

The entire tanning of the skin or hide from the commencement of thepretanning to the completion of the final chrome tanning for ordinaryskins or hides will not take more than about six hours performed in adrum or more than about sixteen hours performed in a paddle.

The primary ingredients or constituents in the pretanning compound andliquor are formaldehyde, or other water soluble aldehyde, and sulphuricor other suitable acid, and the salt or salts employed therein may bevaried.

The process set forth herein may be modified in various ways withoutdeparting from the invention and the principles thereof as defined inthe claims hereinafter.

The invention set forth in the foregoing specification is hereby claimedas follows:

1. The chrome tanning process herein set forth in which the hide afterhaving its flesh and hair removed is tanned into leather by subjectingit to pretanning in a mixture of aldehyde, acid, and salt untilconversion thereof into leather commences and then to final tanning inchrome tanning liquor until it is converted into chrome tanned leather.

2. The chrome tanning process herein set forth in which the hide afterhaving its flesh and hair removed is tanned into leather by subjectingit to pretanning in a mixture of formaldehyde, acid, and salt untilconversion thereof into leather commences and then to final tanning inchrome tanning liquor until it is converted into chrome tanned leather.

3. The herein set forth chrome tanning process, comprising removing theflesh and hair from the hide and deliming its surface, then pretanningthe hide in a mixture of aldehyde, acid, salt, and chromic oxide salt,and any products of reaction thereof, to commence converting it intoleather and thereafter completing the tanning of the hide in chrometanning liquor.

4. The herein set forth chrome tanning process, comprising removing theflesh and hair from the hide and deliming its surface, then pretanningthe hide in a mixture of aldehyde, mineral acid, salt, and chromic oxidesalt, and any products of reaction thereof, to commence converting itinto leather and thereafter completing the tanning of the hide in chrometanning liquor.

5. The herein set forth chrome tanning process, comprising removing theflesh and hair from the hide and deliming its surface, then pretanningthe hide in a mixture of aldehyde, sulphuric acid, salt, and chromicoxide salt, and any products of reaction thereof, to commence convertingit into leather and then completing the tanning of the hide in chrometaming liquor.

6. The herein set forth chrome tanning process in which the hide afterth flesh and hair have been removed therefrom and it has been surface'delimed is subjected to a pretanning liquor containing a mixture offormaldehyde, sulphuric acid, salt, and chromic oxide salt, and anyproducts of reaction thereof, until its tannable substance isset andfixed and c nversion thereof into leather commences, and thereafter thehide thus pretanned is subjected to final tanning in chrome tanningliquor to complete converting its tannable substance into leather.

7. A chrome tanning process in which the hide after its flesh and hairhave been removed is subjected to pretanning in a mixture of chromicoxide salt, sulphuric acid, and aldehyde, and any products of reactionthereof, to set and fix its tannable substance and commence conversionthereof into leather, and thereafter the hide thus pretanned issubjected to final tanning in chrome tanning liquor to completeconverting it into leather.

8. The herein set forth chrome tanning process in which the hide afterits flesh and hair have been removed is subjected to pretanning in amixture of formaldehyde, sulphuric acid, and chromic oxide salt, and anyproducts of reaction thereof, until its tannable substance is set andfixed and conversion thereof into leather commences, and thereafter thehide thus pretanned is subjected to final tanning in chrome tanningliquor to complete converting it into leather.

9. The herein set forth chrome tanning process in which the hide afterits flesh and hair have been removed is subjected to a pretanning liquorcontaining a mixture of formaldehyde, sulphuric.

acid, chromic oxide salt, and neutral salt, and any products of reactionthereof, until its tannable substance is 'set and fixed and conversionthereof into leather commences, and thereafter the hide thus pretannedis subjected to final tanning in chrome tanning liquor to completeconverting its tannable substance into leather.

10. A chrome tanning process in which the hide after it has been limedand unhaired and then surface delimed, is subjected to a pretanningliquor containing a mixture of formaldehyde, sulphuric acid, chromicoxide salt, and neutral salt, and any products of reaction thereof, andthereafter the hide thus pretanned is subjected to final tanninginchrome tanning liquor to convert its tannable substance into leather.

FREDERICK A. VOGEL.

